A carton, box or container is typically made of a paper material, such as cardboard or the like, and includes a plurality of flaps at opposite open ends of the carton which must be folded and connected to provide a closed carton. Such cartons are usually provided in a flat, folded state to a manufacturer who then erects the carton, closes and seals one open end, inserts a desired product and closes and seals the opposite end of the carton.
Machinery for erecting, folding and sealing a carton with a product therein are either intermittent or continuous motion systems. In an intermittent system, the carton is sequentially conveyed to a plurality of positions along an assembly line where the carton is stopped for a predetermined time period at each position so that a desired operation can be performed on the carton. In such a system, since the carton is substantially stationary for a short period of time, machinery can be provided at each position which can be movable with respect to the carton to provide the desired operation.
In a continuous motion system, cartons are continuously in motion, one after another, through the system. As the cartons move through the system, they cooperate with various apparatus which are substantially stationary with respect to the moving cartons and perform the desired operations on the cartons. Continuous motion systems dramatically increase the output approximately 5-10 times that of an intermittent system, but require completely different equipment due to the continuous motion of the cartons.
Cartons are typically closed by folding end flaps of the carton using either a "conventional" or a "reverse fold" method and then securing the flaps together with tape, an adhesive or with some other means. In a conventional folding method, opposite minor end flaps are folded first, followed by a first inside major flap and finally a second outside major flap. In a reverse fold method, the first inside major flap is initially folded, followed by the opposite minor flaps and finally the second outside major flap.
When the carton contains a granular or powdered product, the powder tends to work its way out of the carton between the folded and secured flaps during shipping and handling. One way to prevent such leakage is to provide the carton with an inner liner or pouch, such as a plastic bag. A liner, however, significantly increases the cost of the carton, can make the carton difficult to fill and seal with product and can be difficult to recycle since most users neglect to remove and separate the carton and liner for recycling.
Another way to prevent leakage without providing a liner is to provide a "sift proof" carton, preferably sealed with an adhesive. Sift proof adhesively sealed cartons rely on a predetermined pattern of a substantially quick setting adhesive and proper engagement between respective flaps.
Attempts to provide a sift proof carton for very small grain powders with a conventionally folded adhesive carton have not been successful since such powders leak at the corners as well as at improperly sealed edges. Leakage in a conventionally folded adhesion carton primarily occurs from poor adhesion between the minor flaps and the first inside major flap.
Cartons assembled by a reverse fold method and adhesive provide better sift proof qualities than those assembled by a conventional folding method primarily because the first inside major flap, not the minor flaps, is folded first. Thus better adhesion can be provided between the minor flaps and the first inside major flap, particularly near the corners thereof, to prevent leakage.
Accordingly, with a reverse folded carton, the adhesive must be applied to ensure that no leakage occurs between the first inside major flap and both minor flaps. Existing cartons assembled with an adhesive and in accordance with a reverse fold method are typically provided with the adhesive by means of either a contact or non-contact application head as illustrated in FIGS. 5 and 6, respectively.
With the contact type of adhesive application head of FIG. 5, the adhesive is applied with one or more film contact heads to provide the desired pattern. Such an application head, however, cannot apply adhesive with precision, including adhesive placement and thickness, and frequently results in adhesive being squeezed out of the carton which is not acceptable.
With the non-contact type of adhesive application head of FIG. 6, the adhesive is only applied to the first and second inside and outside major flaps. These existing reverse folded cartons, however, leave small gaps between the edges of the first inside major flap and the minor flaps. Thus, powdered or small grain products can enter and migrate along these gaps to eventually leak out of the corners.
It therefore would be desirable to provide a method and adhesive pattern for providing a reverse folded, sift proof, linerless carton that can be utilized in an intermittent or continuous carton erecting and sealing system and can accommodate a variety of granular and powdered materials without leakage.